There is publicly known a suspension bushing of the type that is used in a connecting portion between a suspension arm and a vehicle body. As this type of bushing, there is known the bushing which has an inner and outer cylinders which are arranged concentrically with each other, an elastic body which provides a connection between these cylinders, and a pair of stoppers which projects in an opposed fashion from the inner and outer cylinders (as an example, see a patent reference 1).
This example is shown in FIG. 6. FIG. 6 is a longitudinal cross sectional view of a suspension bushing taken in the axial direction of an inner cylinder, in which the suspension bushing is provided with the inner cylinder 110, an outer cylinder 120 and an insulator 130.
In a middle portion in the longitudinal direction of the inner cylinder 110, there is provided a pair of inner cylinder side stoppers 140 which has a substantially globular shaped curve and projects outwardly. In a middle portion in the longitudinal direction of the outer cylinder 120, there is provided a pair of outer cylinder side stoppers 150 which projects inwardly in opposed positions to the inner cylinder side stoppers 140. Each of surfaces of the inner cylinder side stoppers 140 and the outer cylinder side stoppers 150 is covered with an elastic body layer.
This suspension bushing is arranged in such a condition that a center axis L0 of the inner cylinder 110 extends in the vertical direction of a vehicle body (in the upward and downward direction of the drawing). The outer cylinder 120 is fixed on the vehicle body and the inner cylinder 110 is mounted on a suspension arm. This type of arrangement of the suspension bushing is referred to as “vertical insertion”. In accordance with movement of the suspension, an input in the vertical direction, an input in the horizontal direction lying at right angles to the vertical direction and an input in the wrenching direction in which the center axis L0 is tilted by a suitable angle θ for example so as to become L1 are applied to the suspension bushing. These vibration inputs are absorbed by an insulator 130, and at the time of the large inputs in the horizontal direction and in the wrenching direction, the inner cylinder side stopper 140 and the outer cylinder side stopper are brought into contact with each other to regulate large displacement.